Truck dumper dust control

ABSTRACT

A truck dumper including a material receiving hopper, a tilt table configured to dump a load from the truck or truck trailer into the material receiving hopper. The invention includes a stilling shed positioned above the material receiving hopper and at least one curtain baffle suspended below the roof of the stilling shed. The curtain baffles are positioned such that there is a gap located near the roof and an upper margin of the at least one curtain baffle through which air can flow. The invention further includes an air exhaust structure configured to exhaust dust laden air from the interior of the stilling shed.

CLAIM TO PRIORITY

This application is a divisional of U.S. application Ser. No. 13/099,492entitled “Truck Dumper Dust Control” filed May 3, 2011, which claims thebenefit of U.S. Provisional Application 61/330,777 entitled “TruckDumper Dust Control” filed May 3, 2010, the entire contents of which areincorporated by reference.

FIELD OF THE INVENTION

The invention relates generally to truck dumpers that are used to emptytrucks of their loads. More particularly, the invention relates to thecontrol of dust that is generated by the unloading of trucks by truckdumpers.

BACKGROUND OF THE INVENTION

Woodchips or brush chips have been used in the paper manufacturingindustry as well as in the manufacturing of particle board and orientedstrand board for many years. For the purposes of this application, theterms “woodchips” and “biomass” should be considered to includewoodchips, brush chips and other forms of biomass that are harvestedfrom forests and wooded areas as well as crops that are grown with thespecific intent for the crops to be harvested for biomass. Woodchips arecommonly produced from forest products that are too small to be used forthe production of lumber and are used as raw materials for theproduction of paper pulp in the paper industry as well as in theproduction of particle board and oriented strand board as mentionedabove. Woodchips are commonly transported by truck. Trucks are usedbecause of the necessity of being able to get the transportation vehicleinto the woods or other areas where the woodchips are produced. Thewooded locations where woodchips are produced are often remote andsubject to regular relocation as the trees or brush that are convertedto woodchips are harvested. Thus, trucks are the preferredtransportation mode for woodchip transport.

Woodchips have a relatively low density as compared to other granularmaterials that are commonly transported by truck. Coal, gravel and sandare much denser and are commonly transported by dump trucks. Woodchips,because of their low density and the fact that they commonly haveirregular sharp edge shapes, do not flow from the inside of a dump truckbed as readily as do coal, gravel or sand. Further, woodchips containmoisture and are often harvested in winter. The moisture and low wintertemperatures can cause the woodchips to freeze to each other and to theinside of the truck and be difficult to remove from the truck. Biomassmaterials may also bridge the width of the truck and impede unloading.

To dump woodchips from a dump truck it is necessary to raise the truckbed to an extreme angle as compared to the angle sufficient to dumpdenser materials from a truck. When this is done in the context oflonger truck beds such as semi-trailers, the extreme angle to which thetruck bed is raised creates a serious risk that the raised truck bedwill topple to one side or the other creating a safety hazard as well asthe possibility of damage or destruction of the truck. Accordingly,truck dumpers are commonly used to empty trucks that are used totransport woodchips or other biomass materials.

A truck dumper includes a large tilt bed onto which the semi-trailercontaining woodchips is positioned. Some truck dumpers operate bytilting only the semi-trailer uncoupled from its tractor, while othertruck dumpers lift the entire tractor-trailer rig together for dumping.

The trailer is secured to the tilting bed platform, for example byclamps, and the tilting platform is raised, typically by hydraulic rams,to a position approaching vertical so that gravity can cause thecontained woodchips or other biomass materials to exit the back of thetruck bed.

Some truck dumpers permit the truck to be driven onto the tilt bed in aforward direction while others require that the truck be backed onto thetilt bed.

In the paper mill, particle board and oriented strand board industries,it is common to control the dust that arises from the dumping ofwoodchips or other biomass by spraying water to clear the dust from theair and cause the dust to sink to the ground. In these industries, thewoodchips or other biomass are processed in such a way that addedmoisture is required. So, the addition of water for dust control doesnot cause a problem and may be a benefit to the production process.

More recently, it has become desirable to burn woodchips or otherbiomass for the production of electrical energy at power plants.Usually, the woodchips or biomass are added to coal that is burned togenerate energy. Because biomass is a renewable resource, it isdesirable to substitute it, at least partially, for fossil fuels such ascoal. Biomass may also come from crop residues, dedicated energyproduction crops, forest and wood processing waste, livestock andpoultry waste and urban waste as well as food processing residues. Theaddition of 15% biomass to coal burned for the production of electricalenergy benefits the energy production industry because the carbonemissions created by this combination are considered to be no more thanthat of natural gas.

In the context of burning biomass for energy, it is undesirable to usewater to control dust because it makes the biomass more difficult toburn, reduces BTU content of the biomass and because moisture in thebiomass tends to increase the likelihood of spontaneous combustionbecause the biomass is stored in a relatively dry state. Spontaneouscombustion is generally not a problem in the paper pulp, particle boardor oriented strand board industries because the woodchips or biomass arecommonly stored in a semi-liquid slurry where the moisture level is toohigh to permit spontaneous combustion.

In addition, wood dust entrained in the air can lead to a dustexplosion. As discussed above wood and wood dust has a low density andfloats in the air more readily than coal dust. When the concentration ofwood dust is right a source of ignition can lead to devastatingexplosion.

Further, the cellulose particles in wood dust are an environmentalpollutant and if breathed can contribute to health problem inindividuals exposed.

SUMMARY OF THE INVENTION

Accordingly, there has arisen a need to control the dust that is createdwhen dumping woodchips or other biomass with a truck dumper,particularly at power plants. Controlling this dust creates anenvironmental benefit, protects the safety of workers in the area andreduces the risk of spontaneous combustion and of dust explosionoccurring because of the woodchip dust being entrained in air.

A truck dumper dust control system in accordance with the presentinvention generally includes a tilt table, a receiving hopper, astilling shed and a dusty air exhaust system.

The tilt table generally includes a platform upon which a loaded truckor semi-trailer is positioned for tilting and dumping. As discussedabove, self-dumping trucks are not utilized for woodchip transportbecause of the high angle required to get the woodchips to exit thetruck bed storage compartment. The platform may be structured to receiveand support a semi-trailer, a semi-trailer and tractor or anon-articulated truck. The semi-trailers utilized for transportingwoodchips are longer and taller than other bulk transport semi-trailersto accommodate a volume of woodchips having a similar weight to a loadof rock or coal. This contributes to efficiency of transport.Semi-trailers utilized to haul woodchips are typically about 40 feetlong with a 10 foot side wall.

The platform also includes a holding device to hold the truck or trailerin place on the platform. The holding device may incorporate bumpers toprevent sideways falling over of the trailer as well as clamps to gripthe truck or trailer structure.

The platform is equipped with hydraulic rams or another means of liftingthe platform to tilt it. Typically, the platform and hydraulic rams arestructured to tilt the platform from a horizontal position to an angleof at least sixty five to seventy degrees to facilitate the exit of thewoodchips or other biomass from the truck.

Side panels may be secured to the platform near the rear end of thetruck to minimize dust dispersion by a crosswind or cross air flowacross the platform and truck during the dumping process according toone embodiment of the invention.

The receiving hopper is an enclosure into which the woodchips or biomassare dumped upon exiting the tilted truck. In accordance with theinvention, the receiving hopper is of an appropriate size to receive theload of woodchips or biomass without significant excess space.

Typically, the receiving hopper is coupled to a conveyor whichtransports the woodchips or biomass from the receiving hopper to theprocessing facility.

In accordance with the invention, a stilling shed is erected above thereceiving hopper. The stilling shed includes, for example, three wallsand a roof. The roof may include a support truss over the opening of thestilling shed. In some embodiments of the invention, an articulatedhydraulic arm may be installed on the top of the stilling shed to assistin freeing woodchips from the truck bed compartment that may have frozenor otherwise not exited the truck. The articulated hydraulic arm mayinclude a pneumatic or hydraulic hammer at its end to free stubbornlystuck or frozen biomass from the truck bed. The articulated arm may beoperated from an operator's cab or remotely from another location.

The opening of the stilling shed is sized to receive the rear end andupper portion of the truck when the truck is in the upright tiltedposition for emptying. The opening allow little space between the truckbed and the sides and top of the stilling shed.

In accordance with an example embodiment of the present invention, aseries of curtain baffles hang from the roof of the stilling shed. Thecurtain baffles may be flexible and can be made of rubber or otherflexible material. The curtain baffles are positioned near the openingof the stilling shed and positioned so that at least one of the curtainbaffles contacts the upper portion of the truck bed when the truck is inthe tilted emptying position.

In accordance with an example embodiment of the invention, the curtainbaffles may be arranged in staggered rows and there may be a spacebetween the upper margin of the curtain baffles and the roof of thestilling shed. The space between the upper margin of the curtain bafflespermits the passage of airflow from the ambient atmosphere into thestilling shed. The passage of inflow of air through the space assiststhe transport of dust laden air that arises from shifting, tumbling andsliding of the biomass as it exits the truck bed. Alternately thebaffles may reach the roof of the stilling shed and an opening in theroof of the stilling shed may be present to permit the passage ofairflow from the ambient atmosphere into the stilling shed. In a furtheralternative the baffle may extend to meet the roof of the stilling shedand an opening of slot may be present in the baffle itself to permit theinflow of ambient air.

In one embodiment of the invention, this gap between the upper margin ofthe curtain baffles and the roof may be approximately six inches orfifteen centimeters. The curtain baffles are positioned so thatwoodchips or other biomass that contact the surface of the baffles slidedown the face of the baffles into the receiving hopper. The volume ofthe stilling shed is minimize to reduce the volume of air that needs tobe exhausted to create an air change within the stilling shed. Anopening in the roof of the stilling shed or through the baffle itselfmay be of similar size.

The minimization of volume is important in the invention because alarger volume in the stilling shed permits a longer residence time fordust within the stilling shed for a given air evacuation and filtrationcapacity. A longer residence time of the dust air mixture creates agreater possibility of escape of dust laden air or of ignition of thedust-air mixture.

The dusty air exhaust structure generally includes ductwork to carrydusty air from the stilling shed and receiving hopper to a bag housewhere the dusty air is filtered so that the dust is captured. The dustyair exhaust structure also includes a blower to draw clean air throughthe bag house into the environment.

In accordance with the present invention, it has been observed that thecapture velocities for wood dust are different from other materials suchas coal dust or rock dust. Because of its low density, wood dust floatsmore readily in the air and creates a greater danger of dust explosionif the source of ignition becomes available when the dust is entrainedin the air.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a truck dumper dust control facilitydepicting a tilt table in both a horizontal and an elevated dumpingposition according to an embodiment of the invention;

FIG. 2 is a sectional view of stilling shed according to an exampleembodiment of the invention;

FIG. 3 is a plan view of an arrangement of baffles according to anexample embodiment of the invention;

FIG. 4 is a sectional view of the opening of a stilling shed accordingto an example embodiment of the invention;

FIG. 5 is a partial cut away perspective view of a bag house accordingto an embodiment of the invention;

FIG. 6 is a sectional view of stilling shed according to another exampleembodiment of the invention; and

FIG. 7 is a sectional view of stilling shed according to another exampleembodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 1, truck dumper 100, in accordance with the presentinvention, generally includes tilt table 102, receiving hopper 104,stilling shed 106 and dusty air exhaust 108.

In one embodiment of the invention, tilt table 102, which is depicted inFIG. 1 both in a horizontal orientation and an elevated tiltedorientation, generally includes platform 110, holding device 112,bumpers 114 and side panels 116. Platform 110 is typically constructedof structural steel or another high strength material and isappropriately sized to receive a truck or truck trailer 118. Holdingdevice 112 secures truck or truck trailer 118 to platform 110 during thedumping process so that truck or truck trailer 118 is inhibited fromfalling sideways. Bumpers 114 may be provided to additionally securetruck or truck trailer 118 to platform 110.

Side panels 116 are secured to platform 110 near the location where therear end 120 of truck or truck trailer 118 is positioned on platform110. Side panels 116 extend upwardly from platform 110 approximately theheight of truck or truck trailer 118. Side panels 116 extend rearwardlyfrom rear end 120 of truck or truck trailer 118 toward receiving hopper104.

Receiving hopper 104 is dimensioned to receive the contents of truck ortruck trailer 118 without substantial excess space. Receiving hopper 104is generally conventional and includes Enclosure 122 and a conveyor (notshown). Conveyor (not shown) is coupled to a processing facility towhich the biomass is directed.

Referring also to FIGS. 2-5, stilling shed 106 is positioned generallyabove receiving hopper 104. Stilling shed 106 generally includes threewalls 124 and roof 126. Referring particularly to FIG. 4, stilling shed106 defines opening 128, which is sized to receive the rear end of truckor truck trailer 118 as can be seen in FIG. 1. The volume of stillingshed 106, in accordance with the invention, is minimized to reduce theneed for air exchange. The volume of stilling shed 106 should be largeenough to contain a dust cloud generated by dumping but notsubstantially larger.

Referring to FIGS. 2, 3 and 5, stilling shed 106 includes one or morecurtain baffles 130. Curtain baffles 130 are suspended from roof 126 ofstilling shed 106 and, in accordance with one embodiment of theinvention, are suspended such that space 134 is present between uppermargin 132 of curtain baffles 130 and roof 126. Space 134 permits thepassage of air above curtain baffles 130. Referring to FIG. 5,alternately, opening 135 in roof 126 near the location at which eachcurtain baffles 130 is suspended from roof 126 may permit passage of airinto stilling shed 106. In a further example embodiment of the inventiondepicted in FIG. 7, opening 135′ may be present in curtain baffles 130.

Referring to FIGS. 2, 3 and 5, in an example embodiment of theinvention, curtain baffles 130 are arranged in four staggered rows 136.Rows 136 include first row 138, second row 140, third row 142 and fourthrow 144.

Referring to FIGS. 2, 3 and 5, first row 138 of curtain baffles 130 arerelatively closely spaced near opening 128. Second row 140 is staggeredrelative to first row 138 and curtain baffles 130 of second row 140 arespaced farther apart. Third row 142, in this example embodiment,includes two curtain baffles 130, staggered to fall within the gaps insecond row 140. Fourth row 144, in this example embodiment, includesthree curtain baffles 130 staggered similarly to second row 140.

Referring again to FIG. 2, curtain baffles 130 of rows 136 are ofvariable lengths. First row 138 being shortest, second row 140 beinglonger than first row 138, third row 142 being longer than second row140 and fourth row 144 being longer than third row 142. At least some ofCurtain baffles 130 are thus arranged to contact rear end 120 of truckor truck trailer 118 as the tilting process proceeds.

Stilling shed 106 may include on roof 126 thereof, an articulatedhydraulic arm 146. Articulated hydraulic arm 146 may include hammer 148to assist in freeing woodchips or other biomass that might not beemptied from truck or truck trailer 118 during tilting. Articulatedhydraulic arm 146 may include operator's cab 150.

Dusty air exhaust 108 generally includes ductwork 152 and air filtrationunit 11. An example embodiment of air filtration unit 11 broadlyincludes plenum enclosure 12, base frame 14, air filtration assembly 15,filtered exhaust duct 16, and air intake duct 17. Access ladder 18 issurrounded by safety cage 20 and leads up to catwalk 22, providingaccess to plenum enclosure 12 through access door 24. Filtered exhaustduct 16 and air intake duct 17 may be attached to an integral withplenum enclosure 12. Air filtration assembly 15 is positioned withinplenum enclosure 12. Plenum enclosure 12 is positioned on base frame 14.

Base 14 may include frame 30, legs 32, and braces 34. Base 14 may varyin size and proportion, depending on the size of the plenum enclosure 12to be supported on base 14. Base 14 can be made of a variety of highstrength, durable materials such as structural steel.

Plenum enclosure 12 may be a large, generally cylindrical structure,ranging from twenty-five to fifty feet in height. Plenum cover or roof36 is positioned over plenum enclosure 12. Dust collection funnel 38tapers downwardly toward dust discharge mouth 40. Funnel 38 ispositioned underneath plenum enclosure 12, residing within the spacebelow base frame 30 and between legs 32 and braces 34.

The air filtration assembly 15 is contained mainly within plenum chamber42. Air filtration assembly 15 comprises an air pressure pump 44,pressurization nozzle input duct 46, nozzle arm 48, and numerous filterelements 50 having air permeable hanging filter media bags or socks 52surrounding filter cages 54. In a typical large capacity air handlingsystem, often employing multiple air filtration units 11, as many astwenty thousand filter bags 52 and twenty thousand wire filter cages 54may be utilized. Air pressure pump 44 is connected to nozzle duct 46.Nozzle arm 48 is positioned beneath nozzle duct 46, and has suctionnozzles 56 opening in a downwardly direction, directed toward bag mouths58 of filter elements 50.

Filter media bags or socks 52 are attached to bag mouths 58. Bag mouths58 are positioned below bag nozzles 56. Bag mouths 58 rest on and aresupported by bag hanger deck 62. Filter media bags 52 are positionedover and supported by wire filter cages 54. Unfiltered air enters airfiltration unit 11 through intake duct 17 so as to be processed throughair filtration assembly 15. Filtered air is expelled from air filtrationunit 11 through filtered exhaust duct 16.

In operation, truck or truck trailer 118 loaded with woodchips or otherbiomass is backed onto platform 110 of tilt table 102 or otherwisepositioned on platform 110 of tilt table 102. Truck or truck trailer 118is secured by holding device 112 and bumpers 114. Tilt table 102 islifting from a generally horizontal position to an angled positionapproximately 65-70 degrees from the generally horizontal position todump the woodchips or other biomass from truck or truck trailer 118 intoreceiving hopper 104.

Side panels 116 inhibit cross air flow across the rear end 120 of truckor truck trailer 118 during the tilting process. Thus, side panels 116minimize the dispersion of dust generated by the dumping process to thesurrounding environment and maintain dust laden air in a location whereit can be exhausted by.

As truck or truck trailer 118 is tilted, truck or truck trailer 118contacts at least one set of curtain baffles 130 or several of curtainbaffles 130 sequentially. Truck or truck trailer 118 first contactsfirst row 138 then second row 140 and then third row 142 and finallyfourth row 144. Curtain baffles 130 assist in containing dust laden airin stilling shed 106 and inhibit excessive tumbling of dust laden air instilling shed 106. Dusty air exhaust 108 is operated to withdraw airfrom stilling shed 106 and receiving hopper 104 during the dumpingprocess. Curtain baffles 130 assist in retaining dust laden air withinstilling shed 106 and receiving hopper 104 until dusty air exhaust 108is able to withdraw the dust laden air from the area within. Space 134between upper margin 132 of curtain baffles 130 and roof 126 permits theintake of ambient air into stilling shed 106 to assist in carrying awaydust laden air from stilling shed 106 and receiving hopper 104.

In the event that woodchips or biomass do not empty from truck or trucktrailer 118 because of being lodged or frozen in truck or truck trailer118. An operator may utilize articulated hydraulic arm 146 and hammer148 to free to lodged woodchips or biomass from truck or truck trailer118. In accordance with the invention, the internal volume of stillingshed 106 is controlled to provide a proper air exchange in order todeliver dust laden air to air filtration assembly 11 for filtration.

Minimization of the volume of stilling shed 106 assists in controllingthe volume of dust laden air generated in the dumping process andpermits control of the size and needed capacity of air filtration unit11.

The present invention may be embodied in other specific forms withoutdeparting from the spirit of the essential attributes thereof;therefore, the illustrated embodiments should be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

1. (canceled)
 2. A method of controlling dust escape during theoperation of a truck dumper, the method comprising: enclosing a materialreceiving hopper of the truck dumper at least partially in a stillingshed having a roof and sidewalls; suspending a first curtain bafflewithin the stilling shed near the roof such that there is a gap locatednear a junction of a top margin of the curtain baffle and the roof;locating the curtain baffle in the stilling shed such that when a truckor truck trailer secured on a tilt table of the truck dumper is raisedto an angled position the curtain baffle contacts a rear portion of thetruck or truck trailer; and exhausting dust laden air from the stillingshed to an air exhaust structure.
 3. The method as claimed in claim 2,further comprising securing panels to the tilt table to at leastpartially enclose the rear portion of the truck or truck trailer; andpositioning the panels to inhibit a cross flow of air proximate the rearportion of the truck or truck trailer and the opening of the stillingshed.
 4. The method as claimed in claim 2, wherein the first curtainbaffle comprises a first row of curtain baffles and the method furthercomprising suspending further second and third rows of curtain baffleswithin the stilling shed near the roof such that there is a gap locatednear a junction of a top margin of the second and third rows of curtainbaffle and the roof.
 5. The method as claimed in claim 4, furthercomprising staggering the first, second and third rows of curtainbaffles relative to each other.
 6. The method as claimed in claim 4,further comprising making the first row of curtain baffles of adifferent length vertically from the third row of curtain baffles andmaking the third row of curtain baffles longer than the first row ofcurtain baffles.
 7. The method as claimed in claim 2, further comprisingsubstantially minimizing the volume of the stilling shed.
 8. The methodas claimed in claim 2, further comprising operably coupling a powerhammer to the truck dumper whereby a portion of the entire load in thetruck or truck trailer can be freed if lodged.
 9. The method as claimedin claim 2, further comprising locating the gap near the junction of theroof and the upper margin of the at least one curtain baffle such thatthe gap comprises a space defined between the upper margin of the atleast one curtain baffle and the roof.
 10. The method as claimed inclaim 2, further comprising locating the gap near the junction of theroof and the upper margin of the at least one curtain baffle such thatthe gap comprises an opening defined by the roof near the upper marginof the at least one curtain baffle.
 11. The method as claimed in claim2, further comprising locating the gap near the junction of the roof andthe upper margin of the at least one curtain baffle such that the gapcomprises an opening defined by the at least curtain baffle near theupper margin of the at least one curtain baffle.
 12. A dust controlsystem for application to a truck dumper, comprising: a stilling shedstructured to be positioned above and at least partially surrounding amaterial receiving hopper of the truck dumper, the stilling shed havingan exterior and an interior, the stilling shed having a roof andsubstantially enclosing the material receiving hopper while having anopening sized and shaped to receive the rear portion of a truck or atruck trailer to be dumped at least partially therethrough; at least onecurtain baffle suspended below the roof and positioned to contact thetruck or truck trailer when a tilt table of the truck dumper is in anangled position such that a load carried within the truck or trucktrailer can exit a rear portion of the truck or truck trailer into thematerial receiving hopper, the at least one curtain baffle beingsupported near the roof of the stilling shed such that there is a gaplocated near a junction of the roof and an upper margin of the at leastone curtain baffle through which air can flow; an air exhaust structurein fluid communication with the stilling shed and that exhausts dustladen air from the interior of the stilling shed; and panels secured tothe tilt table platform positioned to at least partially enclose therear portion of the truck or truck trailer that inhibit a cross flow ofair proximate the rear portion of the truck or truck trailer and theopening of the stilling shed as the platform is shifted between asubstantially horizontal position and the angled position.
 13. The dustcontrol system as claimed in claim 12, wherein the at least one curtainbaffle further comprises at least two rows of curtain baffles.
 14. Thedust control system as claimed in claim 13, wherein the at least tworows of curtain baffles are staggered.
 15. The dust control system asclaimed in claim 13, wherein the at least one curtain baffle furthercomprises at least three rows of curtain baffles including a first rowof curtain baffles nearest the opening of the stilling shed, a secondrow of curtain baffles and a third row of curtain baffles, the third rowof curtain baffles being longer in a vertical dimension than the firstrow of curtain baffles.
 16. The dust control system as claimed in claim12, wherein the volume of the stilling shed is substantially minimized.17. The dust control system as claimed in claim 12, further comprising apower hammer operably coupled to the truck dumper whereby a portion ofthe entire load in the truck or truck trailer can be freed if lodged.18. The dust control system as claimed in claim 12, wherein the gaplocated near a junction of the roof and an upper margin of the at leastone curtain baffle comprises a space defined between the upper margin ofthe at least one curtain baffle and the roof.
 19. The dust controlsystem as claimed in claim 12, wherein the gap located near a junctionof the roof and an upper margin of the at least one curtain bafflecomprises an opening defined by the roof near the upper margin of the atleast one curtain baffle.
 20. The dust control system as claimed inclaim 12, wherein the gap located near a junction of the roof and anupper margin of the at least one curtain baffle comprises an openingdefined through the curtain baffle near the upper margin of the at leastone curtain baffle.